The invention relates to a device for tomographic scanning objects, preferably dental teeth.
Devices and methods for scanning and processing the image data of objects by means of optical coherence tomography (OCT) are known.
A device for scanning and processing the image data of objects in the dental field by means of optical coherence tomography (OCT) reads, for example, is shown in WO 2004/100068 A3.
U.S. Pat. No. 4,837,732A relates to a method and an apparatus for 3D dental registration and display using a triangulation technique in which lines are projected and then observed at a different angle, the line distortion indicating the 3D shape. To enhance resolution the lines are moved. The method as known from U.S. Pat. No. 4,837,732A functions only with opaque specimens, this being the reason why the teeth have to be powdered before scanning. In addition to this, an object has to be illuminated at one angle and observed at another angle, resulting in scanning of very steep flanks not being possible.
Known furthermore are devices providing three-dimensional gauging of objects using Moiré patterns in which a pattern of a first grid is projected by means of a beam of light from a light source onto an object and the light beam reflected by the object is guided through a second grid provided in its optical axis and having the same pattern as the grid for sensing by a sensor so that the sensor senses the light beam reflected by the object with a Moiré pattern resulting from overlying the pattern of the first grid and the pattern of the second grid.
In such a device gauging the object is done by concluding the shape of the surface from the shape of the resulting Moiré pattern.
U.S. Pat. No. 5,714,832 A relates to a a device for precisely positioning a grating, the 3d shape being indicated from the shape of Moiré lines. The lines are shifted and to improve the signal quality narrow-band filtering is employed to obtain information as to the slope of the scanned area.
DE 41 36 002 A1 relates to a moiré contour imaging device involving scanning as is disclosed in the above document U.S. Pat. No. 5,714,832 A with LED illumination.
US 2006/0132802 A1 relates to a system for 3D reconstruction of a surface principle of an object surface employing scanning similar to that as already disclosed in the above document U.S. Pat. No. 4,837,732 A. Polarizers (two linear polarizers turned through 90°) are employed to suppress surface reflections.
Also known are devices which work on the principle of the laser confocal microscope (US 2007/0109559 A1).
In applications with diffuse or translucent surfaces there is the problem that the intensity of the Moiré pattern of the imaged object is very weak as compared to the other light reflected by the object.